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From Brian O'Neill <boneil...@gmail.com>
Subject Re: 1000's of CF's. virtual CFs do NOT workŠ..map/reduce
Date Tue, 02 Oct 2012 13:29:54 GMT
Dean,

Great point.  I hadn't considered that either.  Per my other email, think
we would need a custom partitioner for this? (a mix of
OrderPreservingPartitioner and RandomPartitioner, OPP for the prefix)

-brian

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On 10/2/12 8:35 AM, "Hiller, Dean" <Dean.Hiller@nrel.gov> wrote:

>So basically, with moving towards the 1000's of CF all being put in one
>CF, our performance is going to tank on map/reduce, correct?  I mean, from
>what I remember we could do map/reduce on a single CF, but by stuffing
>1000's of virtual Cf's into one CF, our map/reduce will have to read in
>all 999 virtual CF's rows that we don't want just to map/reduce the ONE
>CF.
>
>Map/reduce VERY VERY SLOW when reading in 1000 times more rows :( :(.
>
>Is this correct?  This really sounds like highly undesirable behavior.
>There needs to be a way for people with 1000's of CF's to also run
>map/reduce on any one CF.  Doing Map/reduce on 1000 times the number of
>rows will be 1000 times slowerŠ.and of course, we will most likely get up
>to 20,000 tables from my most recent projectionsŠ.our last test load, we
>ended up with 8k+ CF's.  Since I kept two other keyspaces, cassandra
>started getting really REALLY slow when we got up to 15k+ CF's in the
>system though I didn't look into why.
>
>I don't mind having 1000's of virtual CF's in ONE CF, BUT I need to
>map/reduce "just" the virtual CF!!!!!  Ugh.
>
>Thanks,
>Dean
>
>On 10/1/12 3:38 PM, "Ben Hood" <0x6e6562@gmail.com> wrote:
>
>>On Mon, Oct 1, 2012 at 9:38 PM, Brian O'Neill <bone@alumni.brown.edu>
>>wrote:
>>> Its just a convenient way of prefixing:
>>> 
>>>http://hector-client.github.com/hector/build/html/content/virtual_keyspa
>>>c
>>>es.html
>>
>>So given that it is possible to use a CF per tenant, should we assume
>>that there at sufficient scale that there is less overhead to prefix
>>keys than there is to manage multiple CFs?
>>
>>Ben
>



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